Jan 2 (Reuters) - Immunodiagnostic Systems Holdings Plc said on Friday it had sold its loss-making haematology business unit to Escalon Medical Corp (ESMC.O), a Nasdaq-listed healthcare company, for 4.2 million euros. The producer of diagnostic testing kits said its Biocode Hycel unit would get payment from Escalon over a period of 48 months from Dec. 31, the date of completion of the deal.